1. Field
Embodiments relate to an apparatus and a method for generating extreme ultra violet radiation.
2. Description of the Related Art
An interferometer is a system which splits light emitted from a light source into two or more beams, creates an optical path length difference between the two or more beams, and observes interfering patterns produced when the split beams recombine. Interferometers are used to measure wavelengths, accurately compare lengths or distances, or compare optical distances. In recent years, the interferometer is also used to inspect surface quality of an optical system.
An extreme ultra violet (EUV) light region is a shorter-wavelength region than a visible light region, and EUV light may improve resolution where diffraction is limited by the magnitude of wavelengths in light-based ultra precision metrology. In addition, if a highly coherent light source can be produced, a wide variety of applications using light interference and diffraction can be achieved.
Since coherence of a high-harmonic EUV light source is superior to that of other types of EUV light source, the high-harmonic EUV light source is used as a light source of a EUV interferometer or a EUV scanning microscope. High-harmonic generation is performed such that a high electric field varying with time is applied to inert gas, such as Ar, Ne or Xe, to ionize electrons to then be moved along the trajectory. The electrons are recombined to then generate light in an EUV band with energy corresponding to a sum of ionized energy and electronic motion energy.